Mycobacterium tuberculosis (Mtb) is an acid-fast gram positive bacillus that causes tuberculosis (TB). TB, and its drug-resistant forms, kills more people than any other infectious disease. In 2013, there were 9.0 million active cases of TB. Of these, 0.48 case million were multidrug-resistant TB (MDR-TB). It is notable that the number of MDR-TB cases tripled from 2009 to 2013. This increase in MDR-TB and extensively drug-resistant TB (XDR-TB) has drawn worldwide attention. Furthermore, HIV-TB co-infection is a serious problem in countries where TB is endemic. HIV positive patients are 26-31 times more likely to develop active TB in comparison to an HIV negative person. Overall, 1.5 million people die every year from this disease.
It has been difficult to eradicate TB even though the infection is treatable. Treatment for TB takes at least 6 months and sometimes up to 2 years. The basic 6-month therapy involves two months of an intensive phase using the quadruple drug regimen consisting of Isoniazid (INH), Rifampicin (RIF), Ethambutol (EMB), and Pyrazinamide (PZA), followed by a 4-month continuous phase consisting of INH and RIF. Often, patients do not comply with the entire regimen due to the high numbers of pills/day and side-effects. The discontinuation of treatment allows resistance to develop. Therefore, there is an immediate need for drugs with improved efficacy and reduced toxicity.